The invention concerns the production of a paper container of a sealable cardboard material, equipped with a reinforcing ring.
In such containers a bottom is inserted into a wound jacket and to the upper cut edge of the open side of the container a reinforcing ring of a synthetic plastic material is applied. The ring is in contact with both the inner and the outer surface of the jacket.
A paper container prepared by a process of the afore-mentioned type is known from French Pat. No. 23 22 802. In that patent, a synthetic plastic ring is applied to the upper cut edge of the container on its open side, which is intended to provide the paper container with a certain stability. This plastic ring may grip the upper cut edge both from the outer and the inner side. The application of this plastic ring utilizes the elastic deformation of the jacket, which is temporarily expanded by means of a suitable mandrel and subsequently contacts the ring. Both the reinforcing ring and the jacket must have a slightly conical configuration such that the upper diameter of the container is smaller than its bottom diameter. The field of application of such a conical paper container is very limited. Furthermore, there is no assurance that an adequate seal is provided between the jacket and the reinforcing ring. Attempts have, therefore, been made to weld the plastic reinforcing ring into the jacket. However, as these rings are relatively thick compared with the wall thickness of the material, there are always difficulties in welding. In the course of the welding process, the plastic rings were plastically deformed and were softened to the extent that they lost their configuration accuracy. Containers of this type and the corresponding preparation process have thus not been accepted in practice.
It is the object of the invention to enable reinforcing rings to be welded tightly to the jacket, without encountering the disadvantages found in actual practice of the deformation of the rings during the welding process.